This invention relates generally to a process for continuously polymerizing a diamine-dicarboxylic acid salt and extruding the resulting polyamide into fibers. More particularly, it involves the control of properties in polyamide fibers through adjustment of process variables.
The continuous preparation of polyamides is known and is described, e.g., in Taylor, U.S. Pat. No. 2,361,717 and Bryan, U.S. Pat. No. 3,357,955. Generally, an aqueous solution of a diamine-dicarboxylic acid salt is concentrated to the desired levels in an evaporator apparatus wherein water is removed. Next, additional water is removed while the salt solution is further concentrated and polymerized at amidation temperatures and pressures in a polymerizer apparatus. Then, the polymer is passed to a finisher apparatus where it is further polymerized and more water is removed. After leaving the finisher apparatus, the molten polymer is pumped through a transfer line (tube) to spinning machine manifolds where it is spun continuously into polyamide fibers.
In such a process, variables can cause undesirable changes in the properties of the final fibers which may not be measured until many pounds of polymer have been produced. Two such properties are dyeability and relative viscosity. An improved process has now been discovered for controlling the dyeability and relative viscosity of polyamide filaments produced from polymer containing unbalanced amine and carboxyl ends.